Electronic commerce is a popular way of selling items, such as digital content items, to consumers. A typical electronic commerce system may generate user interfaces that enable consumers to browse and/or purchase items from a merchant or seller associated with the electronic commerce system. Often, items of digital content, such as audio books, are available in multiple formats. Recommendation components or engines are sometimes used by electronic commerce systems to suggest or recommend items, including items of digital content, to their customers.
Items can be recommended based on purchase or browse histories of users. Recommendation components or engines typically attempt to identify and/or present items that may be of general interest to a given user. For example, an electronic commerce service may provide a list of recommended items for a user that are selected based on a determination that the recommended items are similar to items the given user has purchased or browsed in the past. As another example, some recommendation services may recommend items that have been previously purchased by users with similar interests to the given user. When determining a content item to recommend to a user, a recommendation service can consider information regarding the user, such as information about current and past user behavior.